1. Field of the Disclosure
This specification relates to a rectenna, and more particularly, a wideband rectenna.
2. Background of the Disclosure
A rectenna, which converts radio frequency (RF) energy to direct-current (DC) power, is a key component of free-space microwave power transmission (MPT) systems for the application of microwave powered unmanned aerial vehicle (UAVs), space solar power satellite stations (SSPS) and the like. The constraints on the design of MPT systems are the choice of an operating frequency and a system configuration of a transmitter and a receiver.
Recently, an MPT consisting of an active phased array, a rectenna array system, and a beam controlled system was tested and found to have RF to DC conversion efficiency (ηRF-DC) of 54% at 1 mW RF input for the unit element and 5.8 GHz. This system, which operates for more than 8 hours, has transmitting and receiving array elements with circular polarization, allowing it to obtain high RF-DC conversion efficiency.
In order to design a compact rectenna array, a high operating frequency should be chosen to reduce an area of a receiving array aperture. For this reason, there have been some attempts to design rectennas at 35 GHz and 95 GHz. However, there are limitations such as low RF-DC conversion efficiency and high fabricating costs to develop such high power transmitting and receiving systems.
Therefore, there have been tradeoffs with a compact size and a light weight in terms of choosing an operating frequency for microwave powered aerial vehicle (MPAV) systems, which operate at X-band.